Cryogenic vacuum pumps, or cryopumps, currently available generally follow a common design concept. A low temperature array, usually operating in the range of 4 to 25 K., is the primary pumping surface. This surface is surrounded by a higher temperature radiation shield, usually operated in the temperature range of 60 to 130 K., which provides radiation shielding to the lower temperature array. The radiation shield generally comprises a housing which is closed except a frontal array positioned between the primary pumping surface and a work chamber to be evacuated.
In systems cooled by closed cycle coolers, the cooler is typically a two-stage refrigerator having a cold finger which extends through the rear or side of the radiation shield. High pressure helium refrigerant is generally delivered to the cryocooler through high pressure lines from a compressor assembly. Electrical power to a displacer drive motor in the cooler is usually also delivered through the compressor.
After several days or weeks of use, the gases which have condensed onto the cryopanels, and in particular the gases which are, absorbed, begin to saturate the cryopump. A regeneration procedure must then be followed to warm the cryopump and thus release the gases and remove the gases from the system. As the gases evaporate, the pressure in the cryopump increases, and the gases are exhausted through a relief valve. During regeneration, the cryopump is often purged with warm nitrogen gas. The nitrogen gas hastens warming of the cryopanels and also serves to flush water and other vapors from the cryopump.
Nitrogen is the usual purge gas because it is inert, and is available free of water vapor. It is usually delivered from a nitrogen storage bottle through a fluid line and a purge valve coupled to the cryopump.
After the cryopump is purged, it must be rough pumped to produce a vacuum about the cryopumping surfaces and cold finger to reduce heat transfer by gas conduction and thus enable the cryocooler to cool to normal operating temperatures. The rough pump is generally a mechanical pump coupled through a fluid line to a roughing valve mounted to the cryopump.
Control of the regeneration process is facilitated by temperature gauges coupled to the cold finger heat stations and by pressure gauges. The temperature and/or pressure sensors mounted to the pump are coupled through electrical leads to temperature and/or pressure indicators.
Although regeneration may be controlled by manually turning the cryocooler off and on and manually controlling the purge and roughing valves, a regeneration controller is used in more sophisticated systems. Leads from the controller are coupled to each of the sensors, the cryocooler and motor and the valves to be actuated. In U.S. Pat. No. 4,918,930 entitled xe2x80x9cElectronically Controlled Cryopumpxe2x80x9d by Peter Gaudet, et al., the entire teachings of which are incorporated herein by reference, regeneration control electronics are integrally mounted to the cryopump.
The present invention is predicated on the recognition that there are a number of electronic functions, such as sensing elements, power conditioning modules, controller modules that can be integrated into a cryopump system.
The present invention relates to a cryopump system which includes an integral assembly having a refrigerator, cryopumping surfaces cooled by the refrigerator, a first electronic module for controlling the cryopump, and a second electronic module which is removably coupled to the first electronic module. The second electronic module is removably coupled to the first electronic module with a first surface of the second electronic module abutting a complementary first surface of a housing of the first electronic module. It should be noted that the housing could comprise a housing for the printed circuit boards or in the alternative, a housing into which the electronic controller module can slide into. Preferably, the first controller module housing has three orthogonal surfaces of approximately the same dimensions. Electronic modules can be removably coupled to each of the three surfaces.
Additional electronics can be included in a cryopump system beyond the basic controller module. The additional electronic modules may functionally include, but are not limited to control, monitoring, fault diagnostics, fault detection and fault isolation modules. For example, the modules may comprise sensor modules, power conditioning modules, and network controller modules. Each electronic module can be electrically and mechanically independent or in the alternative, can be electrically dependent on the controller module. It is not sufficient to install the additional electronic modules in one particular location. Different cryopump systems have different functional, packaging and space requirements which dictate different installation configurations. A cryopump system can include one of many electronic additions. The electronic modules of the present invention provide a level of flexibility and selectiveness to tailor the number of components and mounting locations of the components. Thus, the electronic modules facilitate the accommodation of any number and locations of modules into a cryopump system.
In a preferred embodiment, the electronic modules can be removably coupled to each other in a stack configuration. In another preferred embodiment, the electronic modules can be removably coupled to any available surface of the first electronic controller module housing. In another preferred embodiment, the electronic modules are adapted to be mounted on a bracket which can be removably coupled to any available surface in the cryopump system.
One embodiment of the cryopump system further includes a module cap which is coupled to an end of an electronic module to shield electrical connections between two coupled electronic modules. The cryopump system further includes a base cover covering a base portion of the cryopump. A module cap can be coupled to the base cover and connections between two electronic modules extend through the module cap and the base cover.
In a preferred embodiment, the cryopump system includes mechanical connector elements at each end of a surface of an electronic module to connect or couple additional modules to each other. The connector elements may include, but are not limited to, mounting clips and complementary slots. The mounting clips are seated in the complementary slots.
In a preferred embodiment, heat transfer ribs are provided on surfaces of an electronic module that are not used as the mounting surface to another electronic module.
The preferred electronic module comprises a channel of rectangular cross section having slots for mounting printed circuit boards. In a preferred embodiment, there is a standard printed circuit board form factor which is used to standardize the size of the printed circuit boards to be installed into the electronic modules.
The electronic modules can also be mounted remotely, for example in a rack or any available surface of the cryopump system.
The foregoing and other objects, features and advantages of the cryopump system will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.